Overcity

Overcities (or sky cities) were large tower blocks the size of cities constructed on Earth by the Earth Empire during the 30th century. They had large anti-grav engines which allowed them to hover over the polluted, war-torn surface. Half of Earth's population lived in the overcities, the wealthier having access to the higher levels. The poor and aliens lived on the planet's surface in an Undercity. (TV: The Mutants, PROSE: Original Sin)